This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
A communication system is a facility that enables communication between two or more entities such as user terminal equipment and/or networks entities and other nodes associated with the communication system. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on. The communication system can be used for providing the users thereof with various types of services.
The communication may be provided via fixed line and/or wireless communication interfaces. A feature of the wireless communication systems is that they provide mobility for the users thereof. Examples of communication systems providing wireless communication include cellular or mobile communications systems such as the public land mobile network (PLMN) and wireless data networks such the Wireless Local Area Network (WLAN). Examples of the fixed line systems include the public switched telephone network (PSTN) and various fixed line data networks.
There is an increasing demand for mobile communications services, and in particular increasing use of a diversity of mobile communication devices such as laptop computers, personal digital assistant (PDA) equipment such as palm tops and intelligent telephones. In addition to the wide area cellular networks mentioned above which may provide network access for such devices, new, more localized access networks have emerged in recent years. These include, for example, WLAN hotspots which may provide higher speed network access than is available from a cellular network, but only within a geographically restricted area.
Some cellular network operators may in certain cases enable their subscribers to roam into WLAN access networks. This is part of a more general trend where services are provided over a range of different access networks. With this trend comes the additional complexity derived from the need to offer services over radically different bearer types.
In addition to these cellular and WLAN networks which may be offered for public access, there has been a growth in private networks associated with individuals or corporate entities. These private networks may include personal area networks (PAN), comprising a plurality of devices under the control of a single user. Typically the private network contains a user equipment which can connect to an access network, such as mobile telephone equipped with wireless access to a PLMN. The additional devices in the PAN may communicate with the user equipment via wired or wireless connections, and may include, for example, a laptop, PDA, camera etc. Some of these devices may additionally be capable of independently accessing the same, or a different access network (for instance a laptop may alternatively access the internet via DSL). Wireless connections in a PAN may be enabled in a PAN using short range wireless communication systems such as Bluetooth.
In addition to personal area networks associated with a particular individual, localized private networks may be provided in a particular building, such as an office, shopping centre or home, for use by individuals or devices within that locality. Alternatively a private network may be installed in a particular vehicle, to provide high-speed access and to insulate users from problems associated with high physical mobility. The number of such private networks is growing continuously, but they vary in the degree to which they permit access to third parties. For instance, a PAN typically restricts access to a particular user. A private network installed in an office may permit access only to employees or devices associated with the corporate entity to which the office belongs. Likewise, a private network installed in a vehicle may be only for the use of the vehicle owner.
The growth of localized public and private networks could therefore provide new capabilities in terms of enhanced mobility and connectivity for users. However, for its full potential to be realized, the problems associated with integrating heterogeneous control technologies employed by the different networks need to be overcome. Furthermore, the availability of network access could be rapidly enhanced by expanding the accessibility of private networks to third parties. Thus a PAN could provide network access for devices belonging to associates of its owner, or a private network installed in a vehicle could be made available to any passenger traveling in the vehicle.
Typically such private networks may have spare capacity available, but do not offer it to third parties. The reasons for this may include compatibility issues, security or authentication concerns. A major issue which needs to be resolved is the question of how to compensate a private network operator/user for the use of their resources by third parties. Addressing this issue satisfactorily would provide an incentive for private networks to provide such access and thus facilitate the expansion of its provision.
Typically, network operators only grant access to users with whom they have previously signed an agreement. This requires human interaction and potentially negotiation, and thus inevitably results in a substantial delay between the initial access request and provision of a service. For instance, a cellular network provider will have an agreement with a subscriber to whom services are provided, and may have negotiated additional agreements with other entities involved in providing services to the subscriber. This is acceptable in the context of a network whose infrastructure topology does not change rapidly over time. However, this model is not appropriate for providing instant, on-demand access to one of a plurality of heterogeneous networks, where no authorization has previously been obtained.
Providing on-demand access via heterogeneous networks creates its own problems in terms of network management and compensation for entities involved in enabling access to the end user. A particular issue is how to manage a constantly changing network topology and traffic demands. In the context of providing compensation for private network owners, this means that the access network needs to be able to obtain charging and/or topology information associated with a path taken between a user equipment and the access network. For instance, the access network needs to be able to identify which nodes have been involved in relaying a particular communication to or from the access network.
The topology changes in such an arrangement may be similar to those occurring in ad-hoc networks. A wireless or mobile ad-hoc network comprises a series of nodes connected by wireless links. The topology of an ad-hoc network is typically dynamic since nodes are free to move randomly and organize themselves arbitrarily. Such networks may thus be rapidly deployed without relying on a pre-existing network infrastructure, for instance for military communication, as wireless sensor networks, or as temporary networks in the context of a business meeting. WLAN and wireless PAN may be based on an ad-hoc arrangement.
The nodes in an ad-hoc network typically attempt to communicate with each other by relaying packets. However, due to the limited transmission range that is characteristic of nodes in an ad-hoc network, multiple network “hops” are typically needed for one node to exchange data with another node across the network.
In a conventional cellular radio access network, base station locations and cell coverage are typically fixed, at least in the short term. The mobile stations normally communicate directly with a base station, i.e. there is a single hop between the two. However, in multi-hop cellular networks, relay stations may be employed which provide a link between the base station and the mobile station. Communication between the base station and the mobile station can thus be extended by the relay station, which may be fixed or mobile (e.g. other mobile stations subscribing to the cellular network may be used as relay stations). This arrangement can provide additional flexibility in the design, operation and dimensioning of the mobile network.
A common feature between ad-hoc networks, multi-hop cellular networks and other arrangements involving third-party access to local area networks is that they involve the use of relay nodes for forwarding packet data between the access network and a mobile station. Thus in the context described above, one or more nodes or network elements in a private network may act as a relay node for relaying packet data between a third party device and an access network. Typically the relay nodes do not need to interpret the packet data they relay, other than to forward it on to the next node.
In any relay network, it may be advantageous to determine accurate topology information concerning a communication path involving a mobile station and one or more relay nodes. This is particularly so where a private network relays third party data, in order to provide appropriate compensation for the private network. However, known methods for transmitting data in relay networks may suffer from one or more disadvantages in terms of difficulties of obtaining topology information in dynamic arrangements, or inefficient protocol transmission of such information.
There is therefore a need for improved methods for transmitting data between nodes in a communication system. In particular there is a need for an efficient data transmission method suitable for use in relay networks, which facilitates the verification of topology information by an access network. Embodiments of the present invention aim to address one or more of these problems.